Apparatus for regulating transformer voltages



Feb. 17, 1931. F, 3, H HER 1,793,074

APPARATUS FOR REGULATING TRANSFORMER VOLTAGES Filed July 27. 1929 2 Sheets-Sheet l Im e 5 4/12 Jose M Fae/z 6/ Feb. 17, 1931.

F. J. FISCHER 93,074 APPARATUS FOR REGULATING TRANSFORMER VOLTAGES Filed July 27, 1929 2 Sheets-Sheet 2 Patented Feb. 17, 1931 UNITED STATES PATENT OFFICE FRANZ JOSEPH FISCHER, OI DRIESDEN, GERMANY, ASSIGNOR TO THE FIRM KOCH & S'IEBZEL AKTIENGESELLSCHAFT, OF DRESDEN, GERMANY APPARATUS FOR REGULATING TRANSFORMER VOLTAGES Application filed July 27, 1929, Serial No. 381,652, and in Germany July 31, 1928.

My invention relates to apparatus for the stepless regulation of the voltage of a transformer which is changed over during operation. It is an object of my invention to eliminate sparking and other trouble in a transformer of this type.

- To this end I proceed as follows:

A regulating transformer is provided in combination with means for connecting its secondary coil with tappings on the secondary coil of a step transformer the voltage of which is to be regulated. Initially, both ends of the secondary coil in the regulating transformer'are connected with the same tap ping of the secondary coil of the step trans former by means of one switch at each end.

In order to regulate the voltage of the step transformer so that one of the two switches is opened'which is connected with the outall) A step transformer which may be changed over duringoperation has already been proposed in which the changing-over from one step to the other is effectedby means of a powerswitch, the terminals of which are alternately connected with the even and the odd tappings of the step transformer by means of a step selector.-

When changing over from one step to the other the compensating currents are limited by bridging resistances, but still they are very considerable with large transformers so that oil switches are required, particularly if the transformer is operated very frequently. The regulating curve shows considerable steps in proportion to the tapping voltage at a given tapping. Notwithstanding these steps, thecbridging resistances required are very large. Moreover, an excess of voltage will occur in consequence of the voltage steps.

It has also been proposed to regulate the operating voltage of a line supplied by a transformer by connecting the central point of a coil on a rotary regulating transformer of special construction with the system, and connecting the ends of this coil with two successive tap pings of a step transformer. Each half of the coil comprises parts of the secondary and the primary, the secondary being secured on the rotor, and the primary on the stator of the regulating transformer.

It has further been proposed to provide a rotary regulating transformer with two pairs of coils'on its stator and a short circuit coil on its rotor, for stepwise switching in combination with an auxiliary transformer.

In the two last-mentioned systems the rotor is placed in such a position to the stator that the additional voltage is regulated without a step from zero to maximum, with the object of conducting the total current through that switch which is connected with the coils whichihave just been linked, and to render substantially dead the other switch which is to be opened. In both systems, however, con-.

siderable switching powers must be overcome when changing-over from one step of the tapping transformer to the other and, therefore, the excess voltage surges are compara- *tively large.

My apparatus might be combined with a rotary regulating transformer of normal type and this would be favorable as compared with the existing systems which require regulating transformers of special design or an auxiliary transformer, but a rotary regulating transformer is not recommended on'account of its high short-circuiting voltage which is caused by the eccentric arrangement of its primary and secondary coils. In consequence of this the additional voltage of a rotary regulating transformer can be made equal to the voltage between two steps only for a definite power while it is necessary that the step transformer should be regulated for all voltages between no load and maximum load.

If, for instance, a system having a rotary regthe additional voltage of the rotary regulating transformer will vary at a load corresponding to the short-circuit voltage. At a short-circuiting voltage of, say, 40 per cent, and an inductive load equal to cos (p==0.7, thepowers which are generated when changing over from one step to the other, are equal to 40 per cent of the step power so that when changing over sparking will occur in proportion to that power. 1

An ideal apparatus would be one in which the additional voltage is equal as to amount and direction to the voltage between two steps at any power, or the resistance of which is equal to the resistance of the tapped step. This would render possible sparkless switching at any load. But this ideal apparatus is impracticable and it is only possible to reduce the short-circuiting voltage to less than about 15 per cent.

Such low short-circuiting voltages may be attained with a sliding transformer which will be described below. This is due to the concentric arrangement of the coils in a sliding transformer, and the low stray resulting therefrom in the maximum as well as in the zero position. All the same there is still a certain switching power to be changed over which corresponds to the small difference of. the short-circuiting voltages of the step and regulating transformers. The. residual change-over power, which remains at the low or high short-circuiting voltage, may be compractically without sparking.

pensated as follows: At maximum voltage, for instance, when one tapping of the step transformer is connected with the next higher tapping past the sliding transformer, the voltage may be increased by regulating the sliding transformer so as to compensate the voltage drop. Thereby, the power is taken over to the switch of the next higher step from the switch of the lower step and thereby the switch of the lower step' is thrown over Supplementary regulation is effected in a very simple manner by starting the switch before the sliding transformer has arrived in its final p'osi tion, and by moving the switch into closing position only after the sliding transformer has arrived in its final position. The switch is now heldin its closing position until the sliding transformer has attained its nearest final position. During this interval the voltage is regulated back from maximum to Zero, that is, the system voltage now rises without a step from the lower to the higher tapping voltage. The residual voltage drop resulting from the passage of current at the sliding transformer results from the controlling reactance and the ohmic resistance which is' compensated in the zero position by overcompensation or by a short-circuiting switch bridging the secondaiy coil of the sliding transformer.- As, consequently, the voltage drop between the two switches is zero or only small, the two above-mentioned switches which are connected with the ends of thesecondary coil in the sliding transformer may be connected with the following tapping yvitliiout sparking, without a step and without In the drawings afiixed to this specification and forming part thereof diagrams of connections and a transformer plant for single-phase alternating current embodying my invention are illustrated diagrammatically by way of example.

In the drawings Fig. l is a diagram showing a one-phase alternating current system, with a step transformer and a regulating transformer,

Figs. 2 to 9 are diagrams illustrating various positions of the switches at the ends of the secondary coil in the regulating transformer in connection with the several tappings, and

Fig. 10 shows a complete plant having a sliding regulating transformer.

Referring now to the drawings, and first to Figs. 1 to 5, 2a is the incoming and 29 is the outgoing lead of one'wire of a one-phase alternating current system, 24a is the second wire of the system, and 24b is a switch between the incoming and outgoing wires which is normally open. U1 is the available system voltage, and U2 is the consumers voltage which is to beregulated.

11 is the primary and 12 is the secondary coil of a step transformer, the primary coil 11 being under the-available voltage U1. 25 is a switch intermediate the incoming wire 24 and the primary coil 11 of the step transformer, 12 is the secondary coil of the step transformer, with its tappings 13, 14, 15, 16, 17, and 18, and 26 is a reversing switch for alternately connecting one ofthe ends of the secondary coil 12 with the one end of the pri mary coil 11. 30is a sliding'regulating transformer, with a primary coil 19 and a secondary coil 20, the ends of the primary coil 19 being connected with the two central tappings 15 and 16, 21 is one of the two switches which are connected with the ends of.' the secondary coil as described in the introduction, the switch 21 which will be referred to as the preliminary switch, being connected with the outgoing wire 29past the secondary coil 20, a connecting wire 27. and a switch 28, 22 is the second switch referred to which is connected directly with the outgoing wire 29 past 27 and 28, and 23 is a shor't-circuit-ing switch for bridging the ends'of the secondary coil 20. I

In the position illustrated in Fig. 1,- the additional voltage is zero. Current flows from the incoming wire 24:- through switches 25 and 26 to the secondary coil 12 and from the tapping 13 through the switches 22 and 28 to the system wire/29. Ihe switches 21 and 23 are closed.

as indicated by the arrow 0 above its secondary coil 20, so that the voltage at the preliminary switch21 is equal to the voltage at the tapping 14. The preliminary switch 21 may be connected with the tapping 14 without producing sparking. If now the switch 22 were opened as shown in Fig. 4, the power to be cut out by this switch would be proportional to the reactance voltage of the regulating transformer. The voltage drop in the regulating transformer is eliminated by regulating the transformer beyond the voltage of the tapping 14 as shown by the arrow M in Fig. 3. The power is now absorbed by the preliminary switch 21 before the switch 22 is opened so that the switch 22 can now be opened without trouble as shown in Fig. 4. The regulating transformer is'now regulated to zero as indicated by the arrow M 0, Fig.

, 4, reducing the voltage to the value of the tapping 14, so that the switch 22 might be closed. However, this would bring about again a compensation of power corresponding to the voltage drop effected in the zero position of the voltage transformer through the reactance. This voltage drop is compensated by closing the short-circuiting switch 23 so that the switch 22 can now be closed at the tapping 14 without sparking or other trouble, as shown in Fig. 5. Similar operations are performed at the other tappings 15 to 18.

For reducing the voltage the operations described are performed in reversed sequence as shown in Figs. 6 to 9. This reversed sequence, however, may also be used for increasing the voltage if instead of the preliminary switch 21 the switch 22 is opened first. The reduction of the voltage is performed in this case in accordance with Figs. 1 to 5. Reversing can also be effected by reversing the direction of the vector in the secondary coil 12 of the step transformer 11, 12, by throwing the switch 26 over to the lower contact.

Referring now to Fig. 10, the secondary I coil 12 of the step transformer has here been shown as arranged in a circle about a shaft 42, the tappings 13 to 18 being sections of arcs of a circle about the shaft 42 and the switches 21 and 22 being carried on the shaft 42 to rotate with it. 53 is a neutral contacting sector which is connected with the wire from the switch 25 by the wire 53a. The neutral sector cooperates with the preliminary switch 22. 54 is a lug on the switch 22 by which the reversing switch is alternately moved into engagement with a pair of contacts 26a and 26b. The first and the last tappings 13 and 18 are provided with contacting sectors 43 and 48 for the switch 22 only as far as their centres while in the other throughout the length of their respective tappings. The neutral sector 53 has no contacting means for the switch 22.

57, 73, 58, 51, and 52 are concentric annular contact strips surrounding the shaft 42. The inner end of the switch 22 slides on the outermost strip 52, and the inner end of the switch 21 slides on the next inner strip 51. The strip 52 is connected with the wire 27, the switch 28 and the outgoing wire 29. The innor end of the wire 27 is connected with one end of the secondary coil 20 of the regulating transformer which is made as a sliding transformer for the reasons stated, and the inner strip 51 is connected with the other end of the secondary coil 20. The primary coil 19 of the transformer is connected with the central tappings 15 and 16, as shown in Fig. 1.

The secondary coil 20 is secured on a fixed core. 31 and the primary coil 19 is secured on a slide 34, both coils 19 and 20 being arranged concentrically. The switch 23 for short circuiting the secondary coil 20 is operatively connected with the slide 34. Reciprocation is imparted to the slide 34 by means of a pitman rod 33 and a crank 32 on a crank shaft 36 which is held in suitable bearings one of which is constituted by the end of the core 31. 36a is a worm gear on the end of the shaft 36 to which rotation is imparted through the medium of a motor 37. 35 are short-circuiting windings which in the zero position 0 in Figs. 2, 4, 6, and 8 are in line with the secondary coil 20, but in its maximum position M, Figs. 3 and 7, they are outside the secondary coil and make an iron return with the core 31. In the dead centre positions of the crank 32 the sliding transformer 30 is either atits zero position 0 or at its maximum position M. 38 is a dog at the free end of the crank shaft 36 which is illustrated as detached from the shaft, 40 is a ratchet wheel on the shaft 42 which is engaged and rotated by the dog 38 as often as the crank shaft 36 has rotated through 180 degs. I

The motor 37 is controlled by a system comprising two outer wires 37a and 370 and a central wire 37 b. The control of the motor comprises a reversing switch 64, two cutting in coils 65 and 66 and two holding coils 67, 68. The cutting-in coil 65 is connected at one of its terminals with the strip 58 by means of a wire 53a, and at its other end with the lower contact 70 of a contact voltmeter 71, and the cutting-in coil 66 is connected with the strip 57 at one end by means of the wire 57a and at its other end with the upper contact 69 of the voltmeter 71. 72 is a voltage transformer for controlling the voltmeter 71. The primary coil of the transformer is connected with the line wire 240; at one end and with the outgoing wire 29 at its other end. These circuits of the cutting-in coils 65 and 66 are completed by means of the brush 59' at the 1;

switch 22 and the central strip 73 which is gonnected with the central wire 37?) by a wire (3a.

74 is the controlling contact of the voltneter 71, 76 is an overload relay the contacts '75 of which are connected with the contact 74 of the voltmeter 71. In the case of overload the relay 76 renders inactive the voltmeter 71 and the circuits of the cutting-in soils 65 and 66 are broken.

60 is a contacting disk on the shaft 42 which is notched at 61. 62 and 63 are contact brushes which are in contact with the outer edge of the disk 60, but not with its notches.

The brush 62 is connected with one terminaland 26?) are provided for the reversing switch 26. In Fig. 10 the reversing switch is shown engaged with the contacts 26a. It will appear that one of the contacts is connectedwith a section 55 of the strip 58 which is separated from the strip, and the other contact is connected with 58, and that similarly one of the contacts 267) is connected with a separate section '56 of the strip 57 and the other with 57. The separation of the sections 55 and 56 is effected by electrical means in the example illustrated. that is. by deadening the sections 55 and 56. These sections might be 1 mechanically connected to the reversing switch 26 by any suitable means, not shown.

The reason-why the contact strips 43 and 48 at the tappings 13 and 18 extend only as far as the centres of the respective tapping strips, and the neutral strip 53 is without any contacting means for the switch 21, is that the secondary coil 20 of the sliding transformer 30 must be short-circuited when the switch 26 is reversed in order to render inactive the regulation by the sliding transformer 30 within range.

In the position illustrated in Fig. 10 the neutral strip 53 is in contact with the switch 22 and the current flows as in the diagram Fig. 1, from the incoming wire 24 past the switch 25, the wire 53.1, the neutral sector 53, switch 22, strip 52, wire 27 and switch 28, to the outgoing wire 29. The swit'ch'22 is moving idly across the tappings 13 and 18 until it attains one of the sectors 43 and 48. the voltage in the system drops, the lower contact of the voltmeter 71 is closed. This causes the coil 65 to become energized and to cut in the switch 64 for the motor 37 which now rotates the shaft 36 and by the medium of the crank 32 displaces the regulating transformer 30 and through the medium of the switch 38 rotates the shaft 42 until the additional voltage has been attained and the voltmeter 71 which is set for this additional voltage returns to its neutral position. When the voltage increases, the upper contact 69 of the voltmeter is closed whereupon the other cutting-in coil 66 operates the switch 64 to of the tappings 13 to 18 as indicated by the heavy radial lines at the several t appings. In any of these positions the switch 62 is opposite one of the notches 61 in the disk 60. This breaks the circuit of the respective holding coil 67 or 68 andthe switch 64 cuts out the motor 37.

YVhen the shaft 36 is rotated the ratchet wheel 40 and the shaft 42 are left stationary until the shaft 36 has been rotated through about 180 degs. whereupon the dog 38 on the shaft 36 engages the ratchet wheel 40 on the shaft 42 and rotates it through one pitch. As compared with the switching described with reference to the diagrams Figs. 1-9, several switching positions are skipped. There are only two switching positions per step which correspond to the diagrams 2 and 4. The regulation of the transformer in accordance with Figs. 3 and 7 is efiected in one of the dead centre positions of the crank 32, that is, before the transformer arrives at its maximum position, and the switch 22 arrives at the tapping 14. Short circuiting of the secondary coil of the transformer 30 is effected by the short-circuiting switch 23 in the zero or upper dead centre position of the crank 32. While the slide 34 is permanently reciprocated by the crank 32 during a regulating operation, the shaft 42 is operated only twice per rotation of the crank 32. The first operation of the shaft42 causes the switch 22 to make contact with the sector 43 and the switch 21 to assume an intermediate position between the sector 43 and the tapping 14. The second operation causes the switch 22 to assume an intermediate position between the sector 43 and the tapping 14, with the switch 21 in a central position on the tapping 14.

The system has been illustrated for single- .phase alternating current, but it may also be applied to multiple-phase alternating current, and in general I wish it to be understood that I do not desire to be limited to the exact details-of construction shown and described for obviousmodifications will occur to a person skilled in-the art.

In the claims aifixed to this specification no selection of any particular modification of the invention is intended to the exclusion of other modifications thereof and the right to subsequently make claim to any modification not covered by these claims is expressly reserved.

I claim 1. A plant for the stepless regulation of the voltage of a transformer which is changed over during operation, comprising a set of tappings on the secondary coil of said transformer, a regulating transformer, a switch connected with each end of the secondary coil of'said regulating transformer and adapted to be connected with said tappings, and coils on said regulating transformer which are adapted to be displaced coaxially, said regulating transformer having a small short-circuiting voltage which is in conformity, to the extent practicable, with the voltage drop of the steps constituted by said tappings.

2. A plant for the stepless regulation of the voltage of a transformer which is changed over during operation, comprisinga set of tappings on the secondary coil of said transformer, a regulating transformer, a switch connected with each end of the secondary coil of said regulating transformer and adapted to be connected with said tappings, coils on said regulating transformer which are adapt ed to be displaced coaxially, and means for short-circuiting the secondary coil of said regulating transformer, said regulating transformer having a small short-circuiting voltage which is in conformity, to the extent practicable, with the voltage drop of the steps constituted by said tappings.

3. A plant for the stepless regulation of the voltage of a transformer which is changed over during operation, comprising a set of tappings on the secondary coil of said transformer, a regulating transformer, a crank shaft for operating said regulating transformer, a switch connected with each end of the secondary coil of said regulating transformer and adapted to be connected with said tappings, and coils on said regulating transformer which are adapted to bedisplaced coaxially, said regulating transformer having a small short-circuiting voltage which is in conformity, to the extent practicable, with the voltage drop of the steps constituted by said tappings.

4;. A plant for the stepless regulation of the voltage of a transformer which is changed over during operation, comprising a set of tappings on the secondary coil of said transformer, a regulating transformer, a switch connected with each end of the secondary coil of said regulating transformer and adapted to be connected with said tappings, a crank shaft for operating said regulating transformer and for moving saidswitches into their respective following positions after m tating through 180 degs, and coils on said regulating transformer which are adapted to be displaced coaxially, said regulating transformer having a small short-circuiting voltage which is in conformity, to the extent practicable, with the voltage drop of the steps constituted by said tappings.

5. A plant for the stepless regulation of the voltage of a transformer which is changed over during operation, comprising a set of tappings on the secondary coil of said transformer, a circular contact strip connected with each tapping, a regulating transformer, a switch connected with each end of the secondary coil of said regulating transformer, one of said switches being adapted to be rotated in contact with said contact strips, and coils on said regulating transformer which are adapted to be displaced coaxially, said regulating transformer having a small shortcircuiting voltage which is in conformity, to the extent practicable, with the voltage drop of the steps constituted by said tappings.

6. A plant for the stepless regulation of the voltage of a transformer which is changed over during operation, comprising a set of tappings on the secondary coil of said transformer, a circular contact strip connected with each tapping, a regulating transformer, a switch connected with each end of the secondary coil of said regulating transformer, one of said switches being adapted to be rotated in contact with said contact strips, a neutral contact strip for said other switch intermediate the first and the last one of said tappings, and coils on said regulating transformer which are adapted to be displaced coaxially, said regulating transformer having a small short-circuiting voltage which is in conformity, to the extent practicable, with the voltage drop of the steps constituted by said tappings.

7. A plant for the stepless regulation of the voltage of a transformer which is changed over during operation, comprising a set-of tappings on the secondary coil of said transformer, a regulating transformer, a motor for operating said transformer, a reversing switch in the circuit of said motor, a contact voltmeter adapted to control said reversing switch, means for rendering inactive said voltmeter when excess current occurs in the system of said first mentioned transformer, a' switch connected with each end of the secondary coil of said regulating transformer and adapted to be connected with said tappings, and coils on said regulating transformer which are adapted to be displaced coaxially, said regulating transformer having a small short-circuiting voltage which is in conformity, to the extent practicable, with the voltage drop of the steps constituted by said tapp n 8. A plant for the stepless regulation of the voltage of a. transformer which is changed over during operation, comprising a. set of tappings on the secondary coil of said transformer, a regulating transformer, a motor for operating said transformer, a reversing switch in the circuit of'said motor, a contact voltmeter adapted to control said reversingswitch, means for rendering inactive said voltmeter when excess current occurs in the system of said first mentioned transformer, holding coils in connection with said reversing switch, a switch connected-with each end of said regulating transformer and adapted to be connected with said tappings, one of said switches being connected with the outgoing wire across the secondary coil of said regulating transformer, means operatively connected with said switch which is connected across said secondary coil, for controlling said holding coils so that said reversing switch only interrupts the operation of said regulating transformer when said switch which is connected across said secondary coil has been'opened, and coils on said regulating transformer which are adapted to be displaced coaxially, said regulating transformer having a small circuiting voltage which is in conformity, to the extent practicable, with the voltage drop of the steps constituted by said tappings.

9. A plant for the stepless regulation of the voltage of a transformer which is changed over during operation, comprising a set of tappings on the secondary coil of said transformer, a circular contact strip connected with each tapping, a regulating'transformer, a switch connected with each end of the secondary coil of said regulating transformer, one of said switches being adapted to be rotated in contact with said contact strips, a. neutral contact strip for said other switch intermediate the first and the last one of said tappings, a motor for rotating said switches,

a reversing switch in the circuit of said motor, holding coils in connection with said reversing swltch, a rotary contact in operative connection with said rotary switches, and coils on said regulating transformer which are adapted to be displaced coaxially, said regulating transformer having a small shortcircuiting voltage which is in conformity, to the extent practicable, with the voltage drop of the steps constituted by said tappings.

10. A plant for the stepless regulation of the voltage of a transformer which is changed over during operation, comprising a set of tappings on the secondary coil ofsaid. transconnected with said coils, contact strips under the control of said switches and connected with said coils, a reversing switch in said system, separate parts in said last mentioned contact strips WhlCh are adapted to be so controlled that direct displacement of said rotary switches from the tapping corresponding to the highest voltage step to that corresponding to the lowest voltage step is prevented, and coils on saidregulating transformer which are adapted to be displaced coaxially, said regulating transformer having a small short-circuiting voltage which is in conformity, to the extent practicable, with the voltage drop of the steps constituted by said ta ppings.

In testimony whereof I afiix my signature.

FRANZ J QSEPH FISCHER.

former, a regulating transformer, a circular contact strip connected with each tappin a neutral contact strip intermediate the and the last one of the tappings, rotary switches adapted to move with respect to said strips, a motor adapted to rotate said switches, a reversing switch in the circuit of c said motor, cutting-in coils operativel; connected with sald reversing switch, clrcuits 

